This invention relates to hybrid polymer polyols and to a process for the preparation of these hybrid polymer polyols. In addition, the present invention relates to a process for the preparation of polyurethane foams from these hybrid polymer polyols, and to the resultant polyurethane foams prepared from these hybrid polymer polyols.
Various types of filled polyols are known and described in the art. Filled polyols are typically stable dispersions of solid particles in a liquid base polyol. More specifically, the known filled polyols include, for example, polyisocyanate polyaddition (i.e. PIPA) polyols, polyurea and/or polyhydrazodicarbonamide (i.e. PHD) polyols and polymer (i.e. PMPO) polyols.
The basic patents relating to such polymer polyol compositions are Stamberger, U.S. Pat. Re. 28,715 (reissue of U.S. Pat. No. 3,383,351) and U.S. Pat. Re. 29,118 (reissue of U.S. Pat. No. 3,304,273). As described therein, a stable dispersion of polymer particles in a polyol can be produced by polymerizing one or more ethylenically unsaturated monomer dissolved or dispersed in a polyol in the presence of a free radical catalyst.
Since then, numerous patents have issued which describe various advances such as increasing solids contents, decreasing viscosity, enhancing stability, etc. in polymer polyols. These patents include, for example, U.S. Pat. Nos. 3,652,639, 3,823,201, 3,850,861, 3,931,092, 4,014,846, 4,093,573, 4,148,840, 4,172,825, 4,208,314, 4,242,249, 4,342,840, 4,390,645, 4,394,491, 4,454,255, 4,458,038, 4,460,715, 4,550,194, 4,652,589, 4,745,153, 4,997,857, 5,196,476, 5,814,699, 5,990,185, 6,455,603, 7,160,975, 7,179,882, 7,759,423 and Re 32,733 (reissue of U.S. Pat. No. 4,463,107).
It is known that the filled polyols are suitable isocyanate-reactive components for the preparation of polyurethane materials such as foams, elastomers, etc. The two major types of polyurethane foams are termed slabstock foams and molded foams. Slabstock foams are used in the carpet, furniture and bedding industries. Primary uses of slabstock foam are as carpet underlay and furniture padding. In the molded foam area, high resiliency (HR) molded foam is the most common type foam made commercially. HR molded foams are used in the automotive industry for a breadth of applications ranging from molded seats to energy-absorbing padding and the like. As the demand for polymer polyols has increased, and the need for better and improved properties in the polymer polyols has increased, new advances in polymer polyol technology have been achieved.
In spite of advances in reduction in viscosity and increased solids contents of polymer polyols, a need for further improvement in viscosity reduction and increase in solids content has continued to exist. In particular, there is a need for technology in polymer polyols that maximizes viscosity reduction while also providing a viable mechanism to higher solids content, while enhancing the stability of the polymer polyols.
One way of enhancing stability of polymer polyols is by the presence of a minor amount of a graft or addition copolymer formed in situ from growing polymer chains and polyol molecules. Various approaches are known in the art. These typically incorporate small amounts of unsaturation into the polyol in addition to that inherently present in the polyoxyalkylene polyols typically used in forming polymer polyols. Various patents including U.S. Pat. Nos. 3,652,639, 3,823,201, and 3,850,861, British Patent 1,126,025 and Japanese Patent Nos. 52-005887 and 48-101494 utilize this approach. The use of “stabilizer precursors,” also termed a “macromer” that contains a particular level of reactive unsaturation, is based on the expectation that during polymerization, in the preparation of the polymer polyol, adequate amounts of stabilizer will be formed by the addition polymerization of the precursor stabilizer with a growing polymer chain. U.S. Pat. Nos. 4,454,255, 4,458,038 and 4,460,715 describe the general concept of using stabilizer precursors in polymerization.
A pre-formed stabilizer (PFS) is known to be particularly useful for preparing a polymer polyol having a lower viscosity at high solids content. In the pre-formed stabilizer processes, a macromer is reacted with monomers to form a co-polymer composed of macromer and monomers. These co-polymers comprising a macromer and monomers are commonly referred to as pre-formed stabilizers (PFS). Reaction conditions may be controlled such that a portion of the co-polymer precipitates from solution to form a solid. Pre-formed stabilizers may be dispersions having low solids contents (e.g., 3 to 15% by weight). It is preferred that the reaction conditions under which pre-formed stabilizers are prepared are controlled so that the particle size is small, thereby enabling the particles to function as “seeds” in the polymer polyol reaction.
U.S. Pat. Nos. 5,196,476, 5,990,185, 6,013,731, 7,160,975 and 7,776,969 as well as EP 0786480 describe a variety of pre-formed stabilizer composition. In general, these are prepared by polymerizing a macromer and one or more ethylenically unsaturated monomers in the presence of a free-radical polymerization initiator and a liquid diluent in which the pre-formed stabilizer is essentially insoluble.
Stable dispersions of polyurea and/or polyhydrazodicarbonamides in a hydroxyl group containing compound (i.e. PHD polyols) are also known and described in the art. See, for example, U.S. Pat. Nos. 4,089,835, 4,761,434, 4,847,320 and 5,342,855. PHD polyols typically comprise the reaction product of (1) one or more organic polyisocyanates, with (2) one or more polyamines selected from the group consisting of (i) primary and/or secondary amino-group containing di- and/or polyamines, (ii) hydrazines, (iii) hydrazides and (iv) mixtures thereof. PHD polyols are known to result in polyurethane foams having improved combustion resistance.
PIPA (polyisocyanate polyaddition) polyols are another type of polymer filled polyols. U.S. Pat. Nos. 4,452,923, 4,438,252, 4,554,306, 5,292,778 and 7,674,853; GB Patents 2102822 and 2072204; WO 94/12553 and WO 00/73364; and EP 418039 describe various types of PIPA polyols and processes for preparing these PIPA polyols. PIPA polyols are generally the polyaddition reaction products of a polyisocyanate and a low molecular weight compound having a plurality of hydroxyl, primary amine and/or secondary amine groups in the presence of high molecular weight polyols. These polymer filled polyols are also known to be suitable in preparing slabstock and molded foams.
U.S. Pat. No. 7,678,840 discloses reactive systems for cavity filling NVH polyurethane foams which have reduced MDI emissions. These reactive systems comprise a polymethylene poly(phenylisocyanate) having polymeric and monomeric contents within the specified ranges, and isomeric MDI contents within the specified ranges; with an isocyanate-reactive component; in the presence of at least one catalyst and water. A suitable isocyanate-reactive component as described in the working examples comprise a polyol blend having an average molecular weight of about 6425 and an average functionality of about 3.1, which comprised at least one polymer polyol having about 43% SAN solids and at least one amine-initiated polyether polyol.
As discussed above, PHD polyols, PIPA polyols and SAN polymer polyols are all well known in the field of polyurethane chemistry. It is also common knowledge that polyurethane foams may be prepared from these various types of polymer modified polyols. There continues to be a need for further improvements in foam properties, particularly flammability, VOC reduction, etc.
The novel hybrid polymer polyols of the present invention offer distinct advantages that are not available from the present commercially available polymer polyols. These include improved flammability in foams prepared from these novel polymer polyols, and lower VOCs (volatile organic compounds) present in the foams compared to the present commercially available polymer polyols. It was surprisingly found that these advantages could be realized in polymer polyols by substituting either a PHD polyol or a PIPA polyol for a portion of or all of the liquid base polyol (typically a polyether polyol) in the composition of the polymer filled polyol. This has not previously been disclosed or suggested.